with Figs. 7 and 8 and show the
windings for a multipolar motor in the two systems.

[Illustration: FIG. 13.]

[Illustration: FIG. 14.]

[Illustration: FIG. 15.]

These figures show how a motor may be wound so as to be a multiple
phase motor, although the current entering the motor is a simple,
elementary three or two phase current, which can be transformed by
means of a simple three or two phase current transformer, before
entering the motor, such transformers as are used at present in the
Lauffen-Frankfort transmission. But the same principle as that for the
motor may also be applied to transformers themselves, as shown in
Figs. 13 and 14. Fig. 13 shows a set of transformers which are fed by
a simple three-phase current shown in heavy lines, and which gives in
its secondary circuit a multiple phase rotary current. The connections
for the primary circuit of a transformer with six coils are shown
diagrammatically in Fig. 15, the numbers 1 to 6 representing the
succession of the phases. Fig. 14 shows a transformer for a two-phase
current with four leads, transforming into a multiple phase current of
16 leads. The transformer in this figure is a single "interlocked"
transformer in which the fields are magnetically connected and not
independent of each other as in Fig. 13. This has advantages in the
regulation of currents, which do not exist in Fig. 13, but which need
not be entered into here. The transformers used in the Lauffen-Frankfort
transmission are similar, magnetically, to Fig. 14, only that they are
for a simple three-phase current in both primary and secondary
circuits. Attention is also called to the difference in the
connections of secondary circuits in Figs. 13 and 14; in the former
they are connected in a closed circuit similarly to an ordinary closed
circuit armature, while in Fig. 14 they are independent as far as the
currents themselves are concerned, though magnetically their cores are
connected. It is not the intention to enter into a discussion of the
relative values of these various connections, but merely to draw
attention to the wide range of the number of combinations which this
system admits of.--_Electrical World_.

* * * * *

THE LONDON PARIS TELEPHONE.[1]

[Footnote 1: Paper read before the British Association.--_Elec.
Engineer._]

By W.H. Preece, F.R.S.

1. I have already on two occasions, at Newcastle and at Leeds, brought
this subject befor